This invention relates to integrated MOSgated power semiconductor devices, and more specifically relates to a novel circuit which permits rapid turn off of a high side switch which drives a grounded load with low power dissipation for the MOSgated power device.
High side switches employing one or more MOSgated power semiconductor devices with integrated control circuits are well known, such as the IR6000 device manufactured by the International Rectifier Corporation, the assignee of the present invention. When such devices drive an inductive load, as in automotive applications, the MOSgated power device is hard to turn off, and may have to dissipate substantial amounts of power due to inductive current during turn off. Furthermore, when the logic ground for the high side switch is at a different potential than the load circuit ground, the power MOSgated device may be caused to unintentionally conduct and dissipate high power which can destroy the device.
Circuits are known to avoid these problems, but such circuits introduce a new problem, whereby, if the output voltage is below the threshold voltage of that of a control MOSFET which clamps the gate of the main MOSgated power device, the main device cannot be turned on on command.